1. Field of the Invention
The invention relates to an overvoltage protection element with a housing, with at least one overvoltage limiting component which is located in the housing, especially a varistor, with two terminal lugs which are each connected to one pole of the overvoltage limiting component in an electrically conductive manner, especially soldered or welded, and with two connecting elements for electrical connection of the overvoltage protection element to the current path or signal path to be protected, in the normal state of the overvoltage protection element the connecting elements each being in electrically conductive contact with one terminal lug at a time.
2. Description of Related Art
The known overvoltage protection elements are generally made as “protective plugs” which together form an overvoltage protection device with the bottom part of the device. For installation of such an overvoltage protection device which, for example, is designed to protect the phase-routing conductors L1, L2, L3 and the neutral conductor N, and optionally, also the ground conductor PE, in the known overvoltage protection devices, there are the corresponding terminals for the individual conductors on the bottom part of the device. For simple mechanical and electrical contact-making of the bottom part of the device with the respective overvoltage protection element, in the overvoltage protection element, the connecting elements are made as plug pins for which there are corresponding sockets which are connected to the terminals in the bottom part of the device, so that the overvoltage protection element can be easily plugged onto the bottom part of the device. This makes it possible to easily replace a defective overvoltage protection element without the conductors connected to the terminals of the bottom part of the device having to be isolated.
In these overvoltage protection devices, installation and mounting can be carried out very easily and in a time-saving manner due to the capacity of the overvoltage protection elements to be plugged in. In addition, these overvoltage protection devices, in part, still have a changeover contact as the signaller for remote indication of the state of at least one overvoltage protection element and an optical state display in the individual overvoltage protection elements. It is indicated by way of the state display whether the overvoltage limiting component which is located in the overvoltage protection element is still serviceable or not. The overvoltage limiting component here is especially varistors, but depending on the application of the overvoltage protection element gas-filled surge arresters, spark gaps or diodes can also be used.
German Patent DE 42 41 311 C2 discloses the initially described overvoltage protection element. In the overvoltage protection element made as a protective plug, the first connecting element is directly connected via a flexible copper band to the first terminal lug on the varistor, while the second connecting element is connected via a second flexible copper band to a rigid disconnection element whose end facing away from the flexible copper band is connected via a solder point to the second terminal lug of the varistor. The disconnection element is exposed to a force from a spring system which leads to the disconnection element being moved linearly away from the terminal lug when the solder connection is broken so that the varistor is electrically isolated when thermally overloaded. Thus, in the known overvoltage protection element there is a thermal disconnector for monitoring the state of a varistor. By way of the spring system, when the solder connection is broken, a telecommunications contact is activated so that remote monitoring of the state of the overvoltage protection element is possible.
European Patent Application EP 0987803 discloses an overvoltage protection element with a thermal isolating mechanism. In this overvoltage protection element, one end of a rigid, spring-loaded slide is soldered both to the first connecting element and also to a terminal lug which is connected to the varistor in the normal state of the overvoltage protection element. Here, undue heating of the varistor also leads to heating of the solder side so that the slide is withdrawn from the connecting site between the first connecting element and the terminal lug as a result of the force of a spring acting on it; this leads to electrical isolation of the varistor.
The plug-in connecting elements which are formed by the sockets located in the bottom part of the device and the contact pins made on the overvoltage protection element must be able to transmit relatively high pulse currents and short circuit currents. Moreover, the plug-in contacts, i.e., the contact pins and the sockets, are mechanically loaded when the overvoltage protection elements are plugged in and withdrawn so that, in the known overvoltage protection elements, correspondingly stable connecting elements are used which are connected to the terminal lugs by way of solder or weld connections.